Audio Filters Based on Configuration

ABSTRACT

A playback device identifies a first audio filter and a second audio filter. The first audio filter is configured to have a first frequency response and the second audio filter is configured to have a second frequency response. The audio input is processed according to the first audio filter and the second audio filter to produce respective first audio output and second audio output. The first audio speaker renders the first audio output and the second audio speaker renders the second audio output, where the second frequency response of the second audio filter compensates for interference between the first audio output rendered by the first audio speaker and the second audio output rendered by the second audio speaker.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority as acontinuation under 35 U.S.C. §120 to U.S. patent application Ser. No.14/329,501, filed on Jul. 11, 2014, entitled “SYSTEMS, METHODS, ANDAPPARATUS TO FILTER AUDIO”, which is a continuation of U.S. patentapplication Ser. No. 13/333,595, filed on Dec. 21, 2011 (now U.S. Pat.No. 8,811,630), entitled “SYSTEMS, METHODS, AND APPARATUS TO FILTERAUDIO”, the contents each of which are herein incorporated by referencein their entireties for all purposes.

FIELD OF THE DISCLOSURE

The disclosure is related to consumer electronics and, moreparticularly, to systems, methods, and apparatus to filter audio.

BACKGROUND

Audio filter circuits and digital audio filtering are used to achievedesired effects by modifying an audio signal prior to outputting theaudio signal via a speaker. Example uses include attenuating certainfrequencies of the signal to reduce or eliminate undesired backgroundnoises or amplifying frequencies of the signal to emphasize particularelements of the audio signal. Such audio filtering, or equalization(EQ), can affect how the audio is perceived by a listener.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, aspects, and advantages of the presently disclosed technologyare better understood with regard to the following description, appendedclaims, and accompanying drawings where:

FIG. 1 shows an illustration of an example system in which embodimentsof the methods and apparatus disclosed herein can be implemented;

FIG. 2A shows an illustration of an example zone player having abuilt-in amplifier and speakers;

FIG. 2B shows an illustration of an example zone player having abuilt-in amplifier and connected to external speakers;

FIG. 2C shows an illustration of an example zone player connected to anA/V receiver and speakers;

FIG. 3 shows an illustration of an example controller;

FIG. 4 shows an internal functional block diagram of an example zoneplayer;

FIG. 5 shows an internal functional block diagram of an examplecontroller;

FIG. 6 shows an example pair of zone players having mid-tweeter-mid(MTM) speaker arrangements, including audio filters, and configured as astereo pair;

FIG. 7 shows a block diagram of an example audio filter to implement thefirst mid-range filter of FIG. 6;

FIG. 8 shows a block diagram of an example audio filter to implement thesecond mid-range filter of FIG. 6;

FIG. 9 shows a block diagram of an example audio filter to implement thetweeter filters of FIG. 6;

FIG. 10 shows a simplified frequency response of a known MTM speakerarrangement;

FIG. 11 shows a simplified frequency response of an example apparatususing the example audio filters of FIGS. 7-9; and

FIG. 12 is a flowchart representative of example method to implement theexample apparatus and/or the example audio filters of FIGS. 4 and 6-8.

FIG. 13 shows a block diagram of an example audio filter to implementthe first and second mid-range filters of FIG. 6.

In addition, the drawings are for the purpose of illustrating exampleembodiments, but it is understood that the present disclosure is notlimited to the arrangements and instrumentality shown in the drawings.

DETAILED DESCRIPTION I. Overview

Example systems, methods, and apparatus to filter audio are disclosedherein. In some examples, an audio filtering circuit such as a digitalaudio processor filters audio to a mid-tweeter-mid (MTM) speakerconfiguration to reduce or eliminate a narrowing phenomenon normallyexperienced using such a configuration. Example systems, methods, and/orapparatus disclosed herein also provide MTM speaker configurations thatcan be used in different orientations (e.g., vertical and horizontal),where the filtering applied to the audio signals may be different basedon the orientation of the speakers. The example systems, methods, and/orapparatus disclosed herein may be used in combination with amultiple-speaker configuration in which the speakers included in theconfiguration share one or more sources of audio information and playthe audio in synchrony.

Some example systems, methods, and/or apparatus provide first filteringto an audio signal to be output from a first mid-range speaker of an MTMconfiguration and provide second filtering to an audio signal to beoutput from a second mid-range speaker of the MTM configuration toreduce or eliminate the narrowing effect and generally improve (e.g.,objectively and subjectively) the audio consistency between differentphysical locations. Accordingly, such example systems, methods, and/orapparatus provide MTM speaker configurations that are highly flexible interms of types of uses by providing improved audio output quality indifferent orientations. This flexibility allows for potentiallyincreased aesthetics and flexibility in placing the speakers fordifferent uses.

An example embodiment of apparatus implemented in accordance with thepresent disclosure includes first and second audio speakers having firstaudio characteristics, a third audio speaker having second audiocharacteristics, wherein the third speaker is positioned between thefirst and second audio speakers, a first audio filter to process anaudio input signal to have a first frequency response including a firstcutoff frequency, the first audio filter to output a first audio outputsignal to the first audio speaker, and a second audio filter to processthe audio input signal to have a second frequency response to compensatefor interference between the first and second frequency responses causedby a position of the first audio speaker relative to the second audiospeaker.

In some embodiments, the first, second, and third audio speakers includea mid-tweeter-mid speaker arrangement, the second audio filter to have asecond cutoff frequency greater than the first cutoff frequency when themid-tweeter-mid speaker arrangement is oriented horizontally. Someexample apparatus include a digital audio processor to implement thefirst and second audio filters.

In some embodiments, the first audio filter includes a low-frequencyshelf filter, a bandpass shelf filter, and a low-pass filter having thefirst cutoff frequency. In some embodiments, the second audio filterincludes a low-frequency shelf filter, a bandpass shelf filter, alow-pass filter having the second cutoff frequency, an allpass filter,and high-frequency shelf filter. In some such embodiments, the allpassfilter applies a −360 degree phase shift to the audio input signal or toa filtered signal based on the audio input signal. Some embodiments ofan apparatus also include an orientation detector to determine whetherthe first, second, and third speakers are in a first orientation or asecond orientation, where the second audio filter is to apply theallpass filter and high-frequency shelf filter when the first, second,and third speakers are in the first orientation and is to omit theallpass filter and the high-frequency shelf filter when the first,second, and third speakers are in the second orientation.

In some embodiments, the apparatus further includes a network interfaceto receive at least one of the input audio signal, a synchronizationsignal associated with a multiple-device arrangement, or a configurationsignal associated with a multiple-device arrangement. In some suchembodiments, the second speaker is to be positioned on the outside whenin a multiple-device configuration.

Another example apparatus implemented in accordance with the presentdisclosure includes first and second audio speakers having first audiocharacteristics, a third audio speaker having second audiocharacteristics, wherein the first, second, and third speakers arearranged in a mid-tweeter-mid (MTM) configuration, and a digital audioprocessor to filter an audio signal to cause first audio output from thefirst audio speaker to have a dominant frequency response in a firstfrequency range relative to the second audio output from the secondaudio speaker.

In some embodiments, the digital audio filter is to filter the audiosignal to cause the first audio output to have a −360 degree lagrelative to the second audio output. In some embodiments, the firstfrequency range is between a cutoff frequency of the second audio outputand a crossover frequency.

In some embodiments, the first frequency range is based on a spacingbetween the first and second audio speakers. In some embodiments, thedigital audio filter is to cause the first audio output and the secondaudio output to have a substantially equal frequency response when thefirst, second, and third speakers are in a second orientation.

In some embodiments, the apparatus further includes a network interfaceto synchronize the first and second audio output with another audiodevice. In some such embodiments, the network interface is to receive atleast one of the audio signal or a user input.

An example method implemented in accordance with the disclosure includesapplying a first mid-range filter of a mid-tweeter-mid speakerarrangement to a first audio signal, applying a second mid-range filterdifferent from the first mid-range filter to a second audio signal tocompensate for interference caused by a position of a first mid-rangespeaker in the mid-tweeter-mid speaker arrangement relative to a secondmid-range speaker in the mid-tweeter-mid speaker arrangement, andoutputting a filtered audio signal from the second mid-range filter viathe second mid-range speaker.

In some embodiments, the method further includes determining aconfiguration of the mid-tweeter-mid speaker arrangement in amultiple-device arrangement, wherein applying the second mid-rangefilter is based on the configuration. In some such embodiments, applyingthe second mid-range filter includes providing an output audio signalfiltered using the second mid-range filter to an outermost mid-rangespeaker of the mid-tweeter-mid speaker arrangement in themultiple-device arrangement.

In some embodiments, a second frequency response of the second mid-rangefilter has a higher cutoff frequency than a first frequency response ofthe first mid-range filter.

Although the following discloses example systems, methods, and apparatusincluding, among other components, firmware and/or software executed onhardware, it should be noted that such systems, methods, and/orapparatus are merely illustrative and should not be considered aslimiting. For example, it is contemplated that any or all of thesefirmware, hardware, and/or software components could be embodiedexclusively in hardware, exclusively in software, exclusively infirmware, or in any combination of hardware, software, and/or firmware.Accordingly, while the following describes example systems, methods,and/or apparatus, the examples provided are not the only way(s) toimplement such systems, methods, and/or apparatus.

When any of the appended claims are read to cover a purely softwareand/or firmware implementation, at least one of the elements in at leastone example is hereby expressly defined to include a tangible mediumsuch as a memory, digital versatile disk (DVD), compact disc (CD),Blu-ray, and so on, storing the software and/or firmware.

These embodiments and many additional embodiments are described morebelow. Further, the detailed description is presented largely in termsof illustrative environments, systems, procedures, steps, logic blocks,processing, and other symbolic representations that directly orindirectly resemble the operations of data processing devices coupled tonetworks. These process descriptions and representations are typicallyused by those skilled in the art to most effectively convey thesubstance of their work to others skilled in the art. Numerous specificdetails are set forth to provide a thorough understanding of the presentdisclosure. However, it is understood to those skilled in the art thatcertain embodiments of the present disclosure can be practiced withoutcertain, specific details. In other instances, well known methods,procedures, components, and circuitry have not been described in detailto avoid unnecessarily obscuring aspects of the embodiments.

Reference herein to “embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentcan be included in at least one example embodiment of the invention. Theappearances of this phrase in various places in the specification arenot necessarily all referring to the same embodiment, nor are separateor alternative embodiments mutually exclusive of other embodiments. Assuch, the embodiments described herein, explicitly and implicitlyunderstood by one skilled in the art, can be combined with otherembodiments.

II. Example Environment

Referring now to the drawings, in which like numerals can refer to likeparts throughout the figures, FIG. 1 shows an example systemconfiguration 100 in which one or more of the method and/or apparatusdisclosed herein can be practiced or implemented. By way ofillustration, the system configuration 100 represents a home withmultiple zones. Each zone, for example, represents a different room orspace, such as an office, bathroom, bedroom, kitchen, dining room,family room, home theater room, utility or laundry room, and patio.While not shown here, a single zone can cover more than one room orspace. One or more of zone players 102-124 are shown in each respectivezone. A zone player 102-124, also referred to as a playback device,multimedia unit, speaker, and so on, provides audio, video, and/oraudiovisual output. A controller 130 (e.g., shown in the kitchen forpurposes of illustration) provides control to the system configuration100. The system configuration 100 illustrates an example whole houseaudio system, though it is understood that the technology describedherein is not limited to its particular place of application or to anexpansive system like a whole house audio system 100 of FIG. 1.

FIGS. 2A, 2B, and 2C show example illustrations of zone players 200-204.The zone players 200-204 of FIGS. 2A, 2B, and 2C, respectively, cancorrespond to any of the zone players 102-124 of FIG. 1. While certainembodiments provide multiple zone players, an audio output can begenerated using only a single zone player. FIG. 2A illustrates a zoneplayer 200 including sound producing equipment 208 capable of generatingsound or an audio output corresponding to a signal received (e.g.,wirelessly and/or via a wired interface). The sound producing equipment208 of the zone player 200 of FIG. 2A includes a built-in amplifier (notshown in this illustration) and speakers (e.g., a tweeter and twomid-range speakers). In certain embodiments, the zone player 200 of FIG.2A can be configured to play stereophonic audio or monaural audio. Insome embodiments, the zone player 200 of FIG. 2A can be configured as acomponent in a combination of zone players to play stereophonic audio,monaural audio, and/or surround audio. As described in greater detailbelow, in some embodiments, the example zone player 200 of FIG. 2A canalso transmit a second signal to, for example, other zone player(s) inthe same or different zone(s), speaker(s), receiver(s), and so on.Transmission of the second signal can be part of, for example, a systemin which multiple zone players, speakers, receivers, and so on, form anetwork to, for example, present media content in a synchronization ordistributed manner.

The example zone player 202 of FIG. 2B includes a built-in amplifier(not shown in this illustration) to power a set of detached speakers210. The speakers 210 of FIG. 2B can include, for example, any type ofloudspeaker. The zone player 202 of FIG. 2B can communicate a signalcorresponding to audio content to the detached speakers 210 via wiredand/or wireless channels. Instead of receiving and generating audiocontent as in FIG. 2A, the zone player 202 of FIG. 2B receives the audiocontent and transmits the same (e.g., after processing the receivedsignal) to the detached speakers 210. Similar to the example zone player200 of FIG. 2A, in some embodiments the zone player 202 can transmit asecond signal to, for example, other zone player(s) in the same ordifferent zone(s), speaker(s), receiver(s), and so on.

The example zone player 204 of FIG. 2C does not include an amplifier,but allows a receiver 214, or another audio and/or video type devicewith built-in amplification, to connect to a data network 128 of FIG. 1and to play audio received over the data network 128 via the receiver214 and a set of detached speakers 216. In addition to the wiredcouplings shown in FIG. 2C, the detached speakers 216 can receive audiocontent via a wireless communication channel between the detachedspeakers 216 and, for example, the zone player 204 and/or the receiver214. In some embodiments the zone player 202 can transmit a secondsignal to, for example, other zone player(s) in the same or differentzone(s), speaker(s), receiver(s), and so on.

Example zone players include a “Sonos Play:3,” “ZonePlayer® 120,” and“ZonePlayer® 90,” which are offered by Sonos, Inc. of Santa Barbara,Calif. Any other past, present, and/or future zone players canadditionally or alternatively be used to implement the zone players ofexample embodiments disclosed herein. A zone player can also be referredto herein as a playback device, and a zone player is not limited to theparticular examples illustrated in FIGS. 2A, 2B, and 2C. For example, azone player can include a wired or wireless headphone. In otherexamples, a zone player might include a subwoofer. In yet otherexamples, a zone player can include a sound bar. In an example, a zoneplayer can include or interact with a docking station for an Apple iPod™or similar device. In some embodiments, a zone player can relay one ormore signals received from, for example, a first zone player to anotherplayback device. In some embodiments, a zone player can receive a firstsignal and generate an output corresponding to the first signal and,simultaneously or separately, can receive a second signal and transmitor relay the second signal to another zone player(s), speaker(s),receiver(s), and so on. Thus, an example zone player described hereincan act as a playback device and, at the same time, operate as a hub ina network of zone players. In such instances, media contentcorresponding to the first signal can be different from the mediacontent corresponding to the second signal.

FIG. 3 shows an example illustration of a wireless controller 300 in adocking station 302. The controller 300 can correspond to thecontrolling device 130 of FIG. 1. The controller 300 is provided with atouch screen 304 that allows a user to interact with the controller 300,for example, to retrieve and navigate a playlist of audio items, controloperations of one or more zone players, and provide overall control ofthe system configuration 100. In some examples, the wireless controller300 may be used to group zone players into stereo and/or othermultiple-device configurations. In certain embodiments, any number ofcontrollers can be used to control the system configuration 100. Incertain embodiments, there can be a limit on the number of controllersthat can control the system configuration 100. The controllers might bewireless like wireless controller 300 or wired to the data network 128.Furthermore, an application running on any network-enabled portabledevices, such as an iPhone™, iPad™, Android™ powered phone, or any othersmart phone or network-enabled device can be used as a controller byconnecting to the data network 128. An application running on a laptopor desktop PC or Mac can also be used as a controller. Examplecontrollers include a “Sonos® Controller 200,” “Sonos Controller foriPhone,” “Sonos® Controller for iPad,” “Sonos® Controller for Android,“Sonos® Controller for Mac or PC,” which are offered by Sonos, Inc. ofSanta Barbara, Calif. The flexibility of such an application and itsability to be ported to a new type of portable device is advantageous.

Referring back to the system configuration 100 of FIG. 1, a particularzone can contain one or more zone players. For example, the family roomof FIG. 1 contains two zone players 106 and 108, while the kitchen isshown with one zone player 102. Zones can be dynamically configured bypositioning a zone player in a room or space and assigning via thecontroller 130 the zone player to a new or existing zone. As such, zonescan be created, combined with another zone, removed, and given aspecific name (e.g., “Kitchen”), if so programmed. The zone players 102to 124 are coupled directly or indirectly to a data network, such as thedata network 128 shown in FIG. 1. The data network 128 is represented byan octagon in the figure to stand out from other components shown in thefigure. While the data network 128 is shown in a single location, it isunderstood that such a network can be distributed in and around thesystem configuration 100.

Particularly, the data network 128 can be a wired network, a wirelessnetwork, or a combination of both. In some embodiments, one or more ofthe zone players 102-124 are wirelessly coupled to the data network 128based on a proprietary mesh network. In some embodiments, one or more ofthe zone players 102-124 are wirelessly coupled to the data network 128using a non-mesh topology. In some embodiments, one or more of the zoneplayers 102-124 are coupled via a wire to the data network 128 usingEthernet or similar technology. In addition to the one or more zoneplayers 102-124 connecting to the data network 128, the data network 128can further allow access to a wide area network, such as the Internet.

In certain embodiments, the data network 128 can be created byconnecting any of the zone players 102-124, or some other connectingdevice, to a broadband router. Other zone players 102-124 can then beadded wired or wirelessly to the data network 128. For example, a zoneplayer (e.g., any of zone players 102-124) can be added to the systemconfiguration 100 by simply pressing a button on the zone player itself,which enables a connection to be made to the data network 128. Thebroadband router can be connected to an Internet Service Provider (ISP),for example. The broadband router can be used to form another datanetwork within the system configuration 100, which can be used in otherapplications (e.g., web surfing). The data network 128 can also be usedin other applications, if so programmed. Further, in certainembodiments, the data network 128 is the same network used for otherapplications in the household.

In certain embodiments, each zone can play from the same audio source asanother zone or each zone can play from a different audio source. Forexample, someone can be grilling on the patio and listening to jazzmusic via zone player 124, while someone is preparing food in thekitchen and listening to classical music via zone player 102. Further,someone can be in the office listening to the same jazz music via zoneplayer 110 that is playing on the patio via zone player 124. In someembodiments, the jazz music played via zone players 110 and 124 isplayed in synchrony. Synchronizing playback amongst zones allows forsomeone to pass through zones while seamlessly listening to the audio.Further, zones can be put into a “party mode” such that all associatedzones will play audio in synchrony.

In certain embodiments, a zone contains two or more zone players. Forexample, the family room contains two zone players 106 and 108, and thehome theater room contains at least zone players 116, 118, and 120. Azone can be configured to contain as many zone players as desired, andfor example, the home theater room might contain additional zone playersto play audio from a 5.1 channel or greater audio source (e.g., a movieencoded with 5.1 or greater audio channels). If a zone contains two ormore zone players, such as the two zone players 106 and 108 in thefamily room, then the two zone players 106 and 108 can be configured toplay the same audio source in synchrony, or the two zone players 106 and108 can be paired to play two separate sounds in left and rightchannels, for example. In other words, the stereo effects of a sound canbe reproduced or enhanced through the two zone players 106 and 108, onefor the left sound and the other for the right sound. In certainembodiments, paired zone players can play audio in synchrony with otherzone players.

In certain embodiments, three or more zone players can be configured toplay various channels of audio that is encoded with three channels ormore sound. For example, the home theater room shows zone players 116,118, and 120. If the sound is encoded as 2.1 channel audio, then thezone player 116 can be configured to play left channel audio, the zoneplayer 118 can be configured to play right channel audio, and the zoneplayer 120 can be configured to play bass frequencies. Otherconfigurations are possible and depend on the number of zone players andthe type of audio. Further, a particular zone can be configured to playa 5.1 channel audio in one instance, such as when playing audio from amovie, and then dynamically switch to play stereo, such as when playingaudio from a two channel source.

In certain embodiments, two or more zone players can be sonicallyconsolidated to form a single, consolidated zone player. A consolidatedzone player (though made up of multiple, separate devices) can beconfigured to process and reproduce sound differently than anunconsolidated zone player or zone players that are paired, because aconsolidated zone player will have additional speaker drivers from whichsound can be passed. The consolidated zone player can further be pairedwith a single zone player or yet another consolidated zone player. Eachplayback device of a consolidated playback device is preferably set in aconsolidated mode.

According to some embodiments, one can continue to do any of: group,consolidate, and pair zone players, for example, until a desiredconfiguration is complete. The actions of grouping, consolidation, andpairing are preferably performed through a control interface, such asusing controller 130, and not by physically connecting and re-connectingspeaker wire, for example, to individual, discrete speakers to createdifferent configurations. As such, certain embodiments described hereinprovide a more flexible and dynamic platform through which soundreproduction can be offered to the end-user.

Sources of audio content to be played by zone players 102-124 arenumerous. Music from a personal library stored on a computer ornetworked-attached storage (NAS) can be accessed via the data network128 and played. Internet radio stations, shows, and podcasts can beaccessed via the data network 128. Music services that let a user streamand download music and audio content can be accessed via the datanetwork 128. Further, music can be obtained from traditional sources,such as a turntable or CD player, via a line-in connection to a zoneplayer, for example. Audio content can also be accessed through AirPlay™wireless technology by Apple, Inc., for example. Audio content receivedfrom one or more sources can be shared amongst the zone players 102 to124 via the data network 128 and/or the controller 130. Theabove-disclosed sources of audio content are referred to herein asnetwork-based audio information sources. However, network-based audioinformation sources are not limited thereto.

III. Example Playback Device

Referring now to FIG. 4, there is shown an example functional blockdiagram of a zone player 400 in accordance with an embodiment. The zoneplayer 400 of FIG. 4 includes a network interface 402, a processor 408,a memory 410, an audio processing component 412, a module 414, an audioamplifier 416, and a speaker unit 418 coupled to the audio amplifier416. FIG. 2A shows an example illustration of such a zone player. Othertypes of zone players can not include the speaker unit 418 (e.g., suchas shown in FIG. 2B) or the audio amplifier 416 (e.g., such as shown inFIG. 2C). Further, it is contemplated that the zone player 400 can beintegrated into another component. For example, the zone player 400could be constructed as part of a lamp for indoor or outdoor use.

Referring back to FIG. 4, the network interface 402 facilitates a dataflow between zone players and other devices on a data network (e.g., thedata network 128 of FIG. 1) and the zone player 400. In someembodiments, the network interface 402 can manage the assembling of anaudio source or file into smaller packets that are to be transmittedover the data network or reassembles received packets into the originalsource or file. In some embodiments, the network interface 402 canfurther handle the address part of each packet so that it gets to theright destination or intercepts packets destined for the zone player400. Accordingly, in certain embodiments, each of the packets includesan Internet Protocol (IP)-based source address as well as an IP-baseddestination address.

In some embodiments, the network interface 402 can include one or bothof a wireless interface 404 and a wired interface 406. The wirelessinterface 404, also referred to as an RF interface, provides networkinterface functions for the zone player 400 to wirelessly communicatewith other devices (e.g., other zone player(s), speaker(s), receiver(s),component(s) associated with the data network 128, and so on) inaccordance with a communication protocol (e.g., any of the wirelessstandards IEEE 802.11a, 802.11b, 802.11g, 802.11n, or 802.15). Toreceive wireless signals and to provide the wireless signals to thewireless interface 404 and to transmit wireless signals, the zone player400 of FIG. 4 includes one or more antennas 420. The wired interface 406provides network interface functions for the zone player 400 tocommunicate over a wire with other devices in accordance with acommunication protocol (e.g., IEEE 802.3). In some embodiments, a zoneplayer includes both of the interfaces 404 and 406. In some embodiments,a zone player 400 includes only the wireless interface 404 or the wiredinterface 406.

In some embodiments, the processor 408 is a clock-driven electronicdevice that is configured to process input data according toinstructions stored in memory 410. The memory 410 is data storage thatcan be loaded with one or more software modules 414, which can beexecuted by the processor 408 to achieve certain tasks. In theillustrated embodiment, the memory 410 is a tangible machine readablemedium storing instructions that can be executed by the processor 408.In some embodiments, a task might be for the zone player 400 to retrieveaudio data from another zone player or a device on a network. In someembodiments, a task might be for the zone player 400 to send audio datato another zone player or device on a network. In some embodiments, atask might be for the zone player 400 to synchronize playback of audiowith one or more additional zone players. In some embodiments, a taskmight be to pair the zone player 400 with one or more zone players tocreate a multi-channel audio environment. Additional or alternativetasks can be achieved via the one or more software modules 414 and theprocessor 408.

The audio processing component 412 can include one or moredigital-to-analog converters (DAC), an audio preprocessing component, anaudio enhancement component or a digital signal processor, and so on. Incertain embodiments, the audio that is retrieved via the networkinterface 402 is processed and/or intentionally altered by the audioprocessing component 412. In some examples, the audio processingcomponent 412 filters audio signals differently for different speakers418. Further, the audio processing component 412 can produce analogaudio signals. The processed analog audio signals are then provided tothe audio amplifier 416 for play back through speakers 418. In addition,the audio processing component 412 can include necessary circuitry toprocess analog or digital signals as inputs to play from zone player400, send to another zone player on a network, or both play and send toanother zone player on the network. An example input includes a line-inconnection (e.g., an auto-detecting 3.5 mm audio line-in connection).

The audio amplifier 416 is a device that amplifies audio signals to alevel for driving one or more speakers 418. The one or more speakers 418can include an individual transducer (e.g., a “driver”) or a completespeaker system that includes an enclosure including one or more drivers.A particular driver can be a subwoofer (for low frequencies), amid-range driver (middle frequencies), and a tweeter (high frequencies),for example. An enclosure can be sealed or ported, for example.

A zone player 400 can also be referred to herein as a playback device.An example playback device includes a Sonos® Play:3, which ismanufactured by Sonos, Inc. of Santa Barbara, Calif. The Play:3 is anexample zone player with a built-in amplifier and speakers. Inparticular, the Play:3 is a three-driver speaker system that includes atweeter and two mid-range speakers (also referred to as drivers). Whenplaying audio content via the Play:3, the left audio data of a track isoutput from the left mid-range speaker, the right audio data of a trackis output from the right mid-range driver, and the tweeter outputscenter or both left and right audio data for a track. Audio fromInternet radio stations, online music and video services, downloadedmusic, analog audio inputs, television, DVD, and so on, can be playedfrom a Sonos® Play:3. While the Play:3 is an example of a zone playerwith speakers, it is understood that a zone player with speakers is notlimited to one with a certain number of speakers (e.g., three speakersas in the Play:3), but rather can contain one or more speakers. Further,a zone player can be part of another device, which might even serve apurpose different than audio (e.g., a lamp).

IV. Example Controller

Referring now to FIG. 5, there is shown an example controller 500, whichcan correspond to the controlling device 130 in FIG. 1. The controller500 can be used to facilitate the control of multi-media applications,automation and others in a system. In particular, the controller 500 isconfigured to facilitate a selection of a plurality of audio sourcesavailable on the network and enable control of one or more zone players(e.g., the zone players 102-124 in FIG. 1) through a wireless networkinterface 508. According to one embodiment, the wireless communicationsis based on an industry standard (e.g., infrared, radio, wirelessstandards IEEE 802.11a, 802.11b 802.11g, 802.11n, or 802.15). Further,when a particular audio is being accessed via the controller 500 orbeing played via a zone player, a picture (e.g., album art) or any otherdata, associated with the audio source can be transmitted from a zoneplayer or other electronic device to the controller 500 for display.

The controller 500 is provided with a screen 502 and an input interface514 that allows a user to interact with the controller 500, for example,to navigate a playlist of many multimedia items and to controloperations of one or more zone players. The screen 502 on the controller500 can be a liquid crystal display (LCD) screen, for example. Thescreen 500 communicates with and is commanded by a screen driver 504that is controlled by a microcontroller (e.g., a processor) 506. Thememory 510 can be loaded with one or more application modules 512 thatcan be executed by the microcontroller 506 with or without a user inputvia the user interface 514 to achieve certain tasks. In someembodiments, an application module 512 is configured to facilitategrouping a number of selected zone players into a zone group andsynchronizing the zone players for audio play back. In some embodiments,an application module 512 is configured to control the audio sounds(e.g., volume) of the zone players in a zone group. In operation, whenthe microcontroller 506 executes one or more of the application modules512, the screen driver 504 generates control signals to drive the screen502 to display an application specific user interface accordingly.

The controller 500 includes a network interface 508 that facilitateswireless communication with a zone player. In some embodiments, thecommands such as volume control and audio playback synchronization aresent via the network interface 508. In some embodiments, a saved zonegroup configuration is transmitted between a zone player and acontroller via the network interface 508. The controller 500 can controlone or more zone players, such as 102-124 of FIG. 1. There can be morethan one controller for a particular system. Further, a controller canbe integrated into a zone player.

It should be noted that other network-enabled devices such as aniPhone®, iPad® or any other smart phone or network-enabled device (e.g.,a networked computer such as a PC or Mac®) can also be used as acontroller to interact or control zone players in a particularenvironment. In some embodiments, a software application or upgrade canbe downloaded onto a network enabled device to perform the functionsdescribed herein.

In some embodiments, a user can create a zone group including at leasttwo zone players from the controller 500. The zone players in the zonegroup can play audio in a synchronized fashion, such that all of thezone players in the zone group play back an identical audio source or alist of identical audio sources in a synchronized manner such that no(or substantially no) audible delays or hiccups could be heard.Similarly, in some embodiments, when a user increases the audio volumeof the group from the controller 500, the signals or data of increasingthe audio volume for the group are sent to one of the zone players andcauses other zone players in the group to be increased together involume.

A user via the controller 500 can group zone players into a zone groupby activating a “Link Zones” or “Add Zone” soft button, or de-grouping azone group by activating an “Unlink Zones” or “Drop Zone” button. Forexample, one mechanism for ‘joining’ zone players together for audioplay back is to link a number of zone players together to form a group.To link a number of zone players together, a user can manually link eachzone player or room one after the other. For example, assume that thereis a multi-zone system that includes the following zones: Bathroom,Bedroom, Den, Dining Room, Family Room, and Foyer.

In some embodiments, a user can link any number of the six zone players,for example, by starting with a single zone and then manually linkingeach zone to that zone.

In some embodiments, a set of zones can be dynamically linked togetherusing a command to create a zone scene or theme (subsequent to firstcreating the zone scene). For instance, a “Morning” zone scene commandcan link the Bedroom, Office, and Kitchen zones together in one action.Without this single command, the user would need to manually andindividually link each zone. The single command might include a mouseclick, a double mouse click, a button press, a gesture, or some otherprogrammed action. Other kinds of zone scenes can be programmed.

In some embodiments, a zone scene can be triggered based on time (e.g.,an alarm clock function). For instance, a zone scene can be set to applyat 8:00 am. The system can link appropriate zones automatically, setspecific music to play, and then stop the music after a definedduration. Although any particular zone can be triggered to an “On” or“Off” state based on time, for example, a zone scene enables any zone(s)linked to the scene to play a predefined audio (e.g., a favorable song,a predefined playlist) at a specific time and/or for a specificduration. If, for any reason, the scheduled music failed to be played(e.g., an empty playlist, no connection to a share, failed UniversalPlug and Play (UPnP), no Internet connection for an Internet Radiostation, and so on), a backup buzzer can be programmed to sound. Thebuzzer can include a sound file that is stored in a zone player, forexample.

FIG. 6 shows an example pair of zone players 602, 604 havingmid-tweeter-mid (MTM) speaker arrangements, including audio filters, andconfigured as a stereo pair. Either of the example zone players 602, 604may be implemented by the zone player 400 of FIG. 4. In particular, eachof the example zone players 602, 604 includes an audio processingcircuit (e.g., the audio processing circuit 412 of FIG. 4) to implementa set of audio filters, and a plurality of speakers (e.g., the speakers418 of FIG. 4) to implement a corresponding set of speakers or audioreproduction devices.

An MTM speaker arrangement includes two mid-range speakers 606, 608,610, 612 (e.g., speakers having a diameter between about 3.5 inches and6.75 inches, operating in the approximate frequency range of 300-5000Hz) and a high-range speaker, also known as a tweeter 614, 615 (e.g.,3.5 inch diameter or smaller, operating in the approximate frequencyrange of 2,000-20,000 Hz) per zone player 602, 604. The example zoneplayers 602, 604 of FIG. 6 may be oriented horizontally, where thecenters of the mid-range speakers are substantially level in ahorizontal direction, and/or vertically, where the centers of themidrange speakers are substantially aligned in a vertical direction. Theexample mid-range speakers 606, 608 are spaced such that the centers ofthe speakers 606, 608 are approximately one-half wavelength of aselected center frequency (e.g., λ0/2) apart. An example centerfrequency λ0 that may be used to determine the spacing of the examplepairs of mid-range speakers 606, 608 and 610, 612 is 1,000 Hz, which hasa wavelength of about 344 millimeters (e.g., at sea level at about 20degrees Celsius). The example tweeter 614 is positioned between theexample mid-range speakers 606, 608.

The example zone players 602, 604 include respective audio filters 616,618. As mentioned above, the example audio filters 616, 618 may beimplemented using digital audio processing circuitry, such as a digitalaudio processor or other digital processing unit. The following examplewill be described with reference to the example audio filter 616 of FIG.6. However, the description of the audio filter 616 is also applicableto the example audio filter 618. The operation of the example zoneplayers 602, 604 as a stereo pair with respect to the audio filters 616,618 is also discussed below. The example zone players 602, 604 may alsobe operated in other multiple-device arrangements. As used herein“multiple-device” refers to separate sets of speakers, such asmultiple-MTM speaker arrangements, and not merely multiple speakers inthe same device.

The example audio filter 616 of FIG. 6 is an active filter, whichfilters the received audio information prior to amplification. Theexample audio filter 616 includes an audio preprocessing block 620, afirst mid-range filter 622, a second mid-range filter 624, and a tweeterfilter 626. The example audio preprocessing block 620 may include, forexample, audio decoding to decompress and/or otherwise convert an audioinformation (e.g., an audio file) from a storage format (e.g.,compressed) to audio information in a playback format. The audiopre-processing block 620 provides the audio information to the examplefilters 622-626 for processing.

Some MTM speaker arrangements experience a “narrowing” phenomenon, inwhich a listener positioned straight in front of the speakers willexperience the audio differently than a listener positioned to the leftor the right of the speakers. This phenomenon is particularly acute foraudio frequencies around the center frequency f₀ (e.g., the frequency onwhich the spacing of the mid-range speakers is based). In some cases,certain frequencies are completely canceled out in some positionsrelative to the speaker. While this behavior may be desirable in somecircumstances, such as when the MTM speakers are oriented vertically(which reduces reflections and/or echoes off of the ceilings andfloors), such behavior may be undesirable in others, such as when theMTM speakers are oriented horizontally (which results in a limited rangeof positions in which the frequency response is consistent and the audiosounds substantially as intended). Unlike such known MTM speakerarrangements, the example zone players 602, 604 of FIG. 6 reduce oreliminate the narrowing phenomenon and increase the angular audibilityrange (e.g., the range of angles measured from straight in front of thespeaker) in which the frequency response is consistent and the soundsfrom the speakers are heard substantially as intended.

In the example of FIG. 6, the audio filter 616 processes the audio basedon the configuration of the zone player 602 in the stereo pair. Inparticular, the zone player 602 is set up as the left speaker (whenviewing from the front). Additionally, the zone player 602 is configuredwith a horizontal orientation. Thus, the zone player 602 is aware thatthe speaker 606 is the left mid-range speaker and the speaker 608 is theright mid-range speaker for the left zone player 602 of the stereo pair(when viewing from the front). Based on this configuration information,the example audio filter 616 applies a first filtering configuration(e.g., the first mid-range filter 620) to the left (e.g., outer)mid-range speaker 606 and applies a second filtering configuration(e.g., the second mid-range filter 624) to the right (e.g., inner)mid-range speaker 608.

The example audio filter 618 also includes audio preprocessing 628, afirst mid-range filter 630, a second mid-range filter 632, and a tweeterfilter 634. Like the audio filter 616, the audio filter 618 applies thedifferent filtering configurations to the example mid-range filters 610,612 based on configuration information for the zone player 604 (e.g.,physical orientation, status as right/left speaker of a stereo pair,etc.). In the example of FIG. 6, the audio filter 618 applies the firstmid-range filter 630 to the right (e.g., outer) mid-range speaker 612and applies the second mid-range filter 632 to the left (e.g., inner)mid-range speaker 610. The example audio filters 616, 618 result in thezone players 602, 604 steering audio and expanding the angular field ofaudibility relative to known MTM speakers.

FIG. 7 shows a block diagram of an example audio filter 700 to implementthe first mid-range filters 622, 630 of FIG. 6. The example audio filter700 of FIG. 7 receives an audio signal and outputs a filtered audiosignal to a mid-range speaker (e.g., an outer mid-range speaker, themid-range speakers 606, 612 of FIG. 6).

On receiving the input audio signal, a second-order low-frequency (LF)shelf filter 702 is applied. The example second-order LF shelf filter702 has a cutoff frequency of 100 Hz, a quality factor (Q) of 0.707, anda gain of 4.5 dB, and increases the gain of the audio signal forfrequencies below the cutoff frequency. The Q of a filter refers to thedamping and/or resonance of a filter. The resulting signal 703 is thenapplied to a second-order bandpass shelf filter 704, which has a centerfrequency of 1.9 kHz, a Q of 1.2, and a gain of −5.0 dB. The bandpassshelf filter 704 attenuates a band of frequencies centered on 1.9 kHz.The signal 705 from the bandpass shelf filter 704 is input to afourth-order low-pass filter 706, which has a cutoff frequency of 3.0kHz and a Q of 0.5. The example low-pass filter 706 attenuates thesignal for frequencies higher than 3.0 kHz. The signal 707 from thelow-pass filter 706 is input to a second second-order bandpass shelffilter 708. The second bandpass shelf filter 708 has a center frequency12.0 kHz, a Q of 2.0, and a gain of −5.0 dB, and therefore attenuatesfrequencies around the frequency 12.0 kHz.

The resulting signal 709 is input to a second-order allpass filter 710,which has a center frequency of 1.0 kHz and a Q of 0.707. The exampleallpass filter 710 does not substantially amplify or attenuate thesignal, but applies a −360 degree phase shift to the signal 709 togenerate a lagging signal 711. The phase shift applied by the allpassfilter 710 may change for frequencies above and below the centerfrequency of 1.0 kHz. The lagging signal 711 is applied to asecond-order high-frequency (HF) shelf filter 712, which has a cutofffrequency of 800 Hz, a Q of 0.707, and a gain of 8.0 dB. As explainedbelow, the example HF shelf filter 712 provides amplification to theoutput of the example filter 700 to create a higher crossover frequencyfor the first mid-range filter 622 than for the second mid-range filter624 of FIG. 6.

The example signal 713 from the HF shelf filter 712 is output to adynamic bass boost filter 714 and a limiter 716. The example filter 700outputs the filtered signal 717 to an amplifier (e.g., the amplifier416) and/or to a mid-range speaker (e.g., the mid-range speaker 606).

While the example filter blocks 702-716 are shown in the orderillustrated in FIG. 7, the blocks 702-716 may be applied in differentways to achieve identical, similar, or different filtering.Additionally, the example center and/or cutoff frequencies, Q values,and/or gains applied by the example filter blocks 702-716 may bemodified to change a frequency response of the example audio filter 700.

In some examples, the second-order bandpass shelf filter 708, thesecond-order allpass filter 710, and/or the second-order HF shelf 712blocks are omitted or skipped when a zone player 602, 604 is in avertical orientation. In these examples, the audio filter 700temporarily operates similar to the example second mid-range filters624, 632 of FIG. 6 and the MTM narrowing phenomenon may be observed fromthe zone player 602, 604. In some examples, however, the mid-rangefilters 622, 624, 630, 632 are implemented using a different filter suchas the example filter 1300 described below with reference to FIG. 13.The invocation of the example second-order bandpass shelf filter 708,the second-order allpass filter 710, and/or the second-order HF shelf712 may be based on the configuration information (e.g., orientation,participation and/or position in a stereo pair, etc.) for the examplezone player 602, 604.

FIG. 8 shows a block diagram of an example audio filter 800 to implementthe second mid-range filters 624, 632 of FIG. 6. The example audiofilter 800 of FIG. 8 receives an audio signal and outputs a filteredaudio signal to an amplifier and/or to a mid-range speaker (e.g., themid-range speakers 608, 614 of FIG. 6).

On receiving the input audio signal (e.g., the same audio signalreceived by the example filter 700 of FIG. 7 when the filters 700, 800are implemented by the same zone player 602, 604), a second-order LFshelf filter 802 is applied. The example second-order LF shelf filter702 has a cutoff frequency of 100 Hz, a Q of 0.707, and a gain of 4.5dB, and increases the gain of the audio signal for frequencies below thecutoff frequency. Thus, the example LF shelf filter 802 performssubstantially the same filtering as the LF shelf filter 702 of FIG. 7.In some examples, the LF shelf filters 702 and 802 may be combined, inwhich case the resulting signal is provided to the different first andsecond mid-range filters (e.g., the first and second mid-range filters622, 624 of FIG. 6) for further processing.

Continuing with the example of FIG. 8, the signal 803 from the LF shelffilter 802 is then applied to a second-order bandpass shelf filter 804,which has a center frequency of 1.9 kHz, a Q of 1.2, and a gain of −5.0dB. The bandpass shelf filter 804 attenuates a band of frequenciescentered on 1.9 kHz. Thus, the example bandpass shelf filter 804performs substantially the same filtering as the bandpass shelf filter704 of FIG. 7. In some examples, the bandpass shelf filters 704 and 804may be combined (e.g., additionally or alternatively to combining the LFshelf filters 702, 802), in which case the resulting signal from thecombined bandpass shelf filter is provided to the different first andsecond mid-range filters (e.g., the first and second mid-range filters622, 624 of FIG. 6) for further processing.

Continuing with the example of FIG. 8, the signal 805 from the bandpassshelf filter 804 is input to a fourth-order low-pass filter 806, whichhas a cutoff frequency of 1000 Hz and a Q of 0.5. The example low-passfilter 806 attenuates the signal for frequencies higher than 1000 Hz.The example signal 809 from the low-pass filter 806 is output to adynamic bass boost filter 808 and a limiter 810. The example filter 800outputs the filtered signal 811 to an amplifier (e.g., the amplifier416) and/or to a mid-range speaker (e.g., the mid-range speaker 608).

FIG. 9 shows a block diagram of an example audio filter 900 to implementthe tweeter filters 626, 634 of FIG. 6. The example audio filter 900 ofFIG. 9 receives an audio signal and outputs a filtered audio signal to atweeter (e.g., the tweeters 614, 615 of FIG. 6).

On receiving the input audio signal (e.g., the same audio signalreceived by the example filters 700, 800 of FIGS. 7 and 8), afourth-order high-pass filter 902 is applied. The example high-passfilter 902 has a cutoff frequency of 3.0 kHz and a Q of 0.5, andattenuates the input audio signal for frequencies lower than 3.0 kHz.The signal 903 output from the high-pass filter 902 is input to a firstsecond-order bandpass shelf filter 904, which has a center frequency of5.0 kHz, a Q of 2.0, and a gain of −5.0 dB. The first bandpass shelffilter 904 attenuates a band of frequencies centered on 5.0 kHz. Theresulting signal 905 is input to a second second-order bandpass shelffilter 906. The example second bandpass shelf filter 906 has a centerfrequency of 8.1 kHz, a Q of 1.0, and a gain of 4.0 dB. Thus, theexample bandpass shelf filter 906 amplifies a band of frequenciescentered on 8.1 kHz.

The example signal 907 from the low-pass filter 906 is output to adynamic bass boost filter 908, a 1-sample delay 910, a signal amplifier(gain) 912 and a limiter 914 The example filter 900 outputs the filteredsignal 917 to an amplifier (e.g., the amplifier 416) and/or to amid-range speaker (e.g., the tweeter 614 of FIG. 6).

Any or all of the example filters 700, 800, 900 of FIGS. 7-9 may beimplemented using one or more digital audio processors, discrete digitaland/or audio components, and/or any other type of logic circuit and/oranalog filters.

FIG. 10 shows a simplified frequency response 1000 of a known MTMspeaker arrangement. The frequency response 1000 of FIG. 10 includes amid-range response 1002 (representative of the mid-range speakers) and ahigh-range frequency response 1004 (representative of the tweeter). At acrossover frequency f_(x), the mid-range response 1002 and thehigh-range response 1004 are substantially equal. The mid-range response1002 dominates in audio frequencies below the crossover frequency f_(x)and the high-range response 1004 dominates in audio frequencies abovethe crossover frequency f_(x). As a result, the λ₀/2 distance betweenthe mid-range speakers causes destructive interference to occur forfrequencies around the center frequency f₀ outside of an angularaudibility range. The destructive interference causes substantialchanges in the objective and subjective perceptions of the audio betweendifferent physical locations inside and outside of the angularaudibility range.

FIG. 11 shows a simplified frequency response 1100 of the exampleapparatus (e.g., the zone player 602, 604 of FIG. 6) using the exampleaudio filters of FIGS. 7-9. The example zone player 602, 604 of FIG. 6reduces or avoids the destructive interference experienced by known MTMspeaker arrangements, thereby increasing the angular audibility rangeand decreasing distortion of the audio between different physicallocations.

The example frequency response 1100 includes a first mid-range frequencyresponse 1102, a second mid-range frequency response 1104, and ahigh-range frequency response 1106. The example first mid-rangefrequency response 1102 corresponds to the mid-range speaker(s) coupledto the first mid-range filters of FIG. 6 (e.g., the mid-range speakers606, 612). The example second mid-range frequency response 1104corresponds to the mid-range speaker(s) coupled to the second mid-rangefilters of FIG. 6 (e.g., the midrange speakers 608, 610). The examplehigh-range frequency response 1106 corresponds to the tweeters 614, 615.

As illustrated in FIG. 11, the mid-range frequency responses 1102, 1104have different crossover frequencies. The cutoff frequency f_(c2) forthe example second mid-range response 1104 is lower than the centerfrequency f₀ on which the mid-range speaker spacing is based. Therefore,at frequencies around the center frequency f₀, the first mid-rangespeakers 606, 612 has the dominant response and the destructiveinterference is substantially reduced. As used herein, a dominantresponse refers to a first frequency response being substantiallystronger (e.g., 3 dB greater or more) than a second frequency response.As a result, the frequencies around the center frequency f₀ have reducedor eliminated interference outside of the angular audibility range. Thecombination of responses 1102, 1104 and the response 1106 have acrossover frequency of f_(x1), which in some examples is higher than thecrossover frequency f_(x) of known MTM crossover frequencies.

The example frequency response 1100 of FIG. 11 is achieved by filteringthe signal to the first mid-range speakers 606, 612 using thefourth-order low-pass filter 706, the allpass filter (e.g., allpassfilter block 710 of FIG. 7) and the HF shelf filter (e.g., thesecond-order HF shelf filter 712). The example low-pass filter 706 hasan increased cutoff frequency relative to known MTM crossover filtersand relative to the low-pass filter 806 used in the example secondmid-range filter 800. As a result, the attenuation of the 1000 Hz-3.0kHz frequency range is reduced or avoided by the signal to the firstmid-range speakers 606, 612 and applied to the signal to the secondmid-range speakers 608, 610.

The example HF shelf filter 712 of FIG. 7 provides additional gain forthe first mid-range speakers 606, 612 above the cutoff frequency f_(c2)of the response. Because the second mid-range speakers 608, 610 aresubstantially attenuated above the cutoff frequency f_(c2) (e.g., 1000Hz-3.0 kHz), the first mid-range filter 700 includes the example HFshelf filter 712 to provide a more consistent response for thefrequencies provided by the mid-range speakers 606, 612. In contrast, ifthe HF shelf filter 712 was not present (or not used), the frequenciesabove the cutoff frequency f_(c2) would sound substantially attenuatedin every physical location.

The use of allpass filter in a first signal and omission in a secondsignal causes the example zone players 602, 604 to steer the audiooutward. As used here, outward refers to steering the audio from theleft zone player 602 toward the left and steering the audio from theright zone player 604 toward the right. Steering the audio furtherdecreases the narrowing effect compared to known MTM speakerarrangements.

FIG. 12 is a flowchart representative of example method 1200 toimplement the example zone players and/or the example audio filters ofFIGS. 4 and 6-8. The example method 1200 may be used to provide an MTMspeaker arrangement having improved audio characteristics in ahorizontal orientation. The example method 1200 may be performed by alogic circuit such as a microprocessor, a digital audio processor,and/or any other type of logic circuit.

The example method 1200 begins by determining (e.g., via an orientationdetector, the accelerometer 422 of FIG. 4) an orientation of an MTMspeaker arrangement (e.g., the zone players 400, 602, 604 of FIGS. 4 and6) (block 1202). For example, the accelerometer 422 determines whetherthe zone player 400, 602, 604 is in a vertical arrangement or ahorizontal arrangement. The example method 1200 also determines (e.g.,via the network interface 402, the processor 408, and/or the memory 410of FIG. 4) a configuration of the zone player 400, 602, 604 in amultiple-device arrangement (block 1204). For example, the processor 408may determine whether the zone player 400, 602, 604 is the left speakeror the right speaker of a stereo speaker arrangement.

The example method 1200 receives an audio signal to be played (block1206). The example audio signal may be compressed and/or encoded audiofrom an audio source, or may be an uncompressed and/or decoded audiosignal. The example method 1200 splits into two portions that mayoperate substantially simultaneously (e.g., via a multi-threading and/ormulti-core processor) or sequentially. In a first branch, the zoneplayer 400, 602, 604 determines whether it is in a horizontalorientation (block 1208). If the zone player 400, 602, 604 is in ahorizontal orientation (block 1208), a first audio filter (e.g., theexample audio processing circuit 412 of FIG. 4, the example audiofilters 616, 618 via the first mid-range filter 622, 630, 700 of FIGS. 6and 7) is applied to the first audio signal (block 1210). For example,the audio processing circuit 412 may apply the first mid-range filter700 of FIG. 7 to the second audio signal. An example second audio filter(e.g., the example audio processing circuit 412 of FIG. 4, the exampleaudio filters 616, 618 via the second mid-range filter 624, 632, 800 ofFIGS. 6 and 8) is applied to the second audio signal (block 1212). Forexample, the audio processing circuit 412 may apply the second mid-rangefilter 800 of FIG. 8 to the second audio signal.

After applying the appropriate filters to the first and second audiosignals (blocks 1208-1214), the example method 1200 applies a tweeterfilter (e.g., the tweeter filter 626, 634 of FIG. 6) to a third audiosignal (block 1216). Based on the configuration (e.g., left/rightspeaker in a multiple-device arrangement) and/or the orientation (e.g.,horizontal or nonhorizontal orientation), the example method 1200outputs the first filtered audio signal to the first mid-range speaker(e.g., the first mid-range speakers 606, 612 of FIG. 6), outputs thesecond filtered audio signal to the second mid-range speaker (e.g., thefirst mid-range speakers 608, 610), and outputs the third filtered audiosignal to the tweeter speaker (e.g., the tweeter speakers 614, 615)(block 1218). Thus, when the example zone player 400, 602, 604 is in ahorizontal orientation, the first and second mid-range speakers outputaudio signals that are filtered differently. For example, the frequencyresponse of the first and second midrange speakers may be similar to thesimplified frequency response illustrated in FIG. 11.

After applying the appropriate filters to the first and second audiosignals (blocks 1208-1214), the example method 1200 applies a tweeterfilter (e.g., the tweeter filter 626, 634 of FIG. 6) to a third audiosignal (block 1216). Based on the configuration (e.g., left/rightspeaker in a multiple-device arrangement) and/or the orientation (e.g.,horizontal or nonhorizontal orientation), the example method 1200outputs the first filtered audio signal to the first mid-range speaker(e.g., the first mid-range speakers 606, 612 of FIG. 6), outputs thesecond filtered audio signal to the second mid-range speaker (e.g., thefirst mid-range speakers 608, 610), and outputs the third filtered audiosignal to the tweeter speaker (e.g., the tweeter speakers 614, 616)(block 1218). Thus, when the example zone player 400, 602, 604 is in ahorizontal orientation, the first and second mid-range speakers outputaudio signals that are filtered differently. For example, the frequencyresponse of the first and second mid-range speakers may be similar tothe simplified frequency response illustrated in FIG. 11.

The example method 1200 may then end and/or iterate to output additionalaudio signals. The example method 1200 may monitor the orientationand/or the configuration of the example zone player 400, 602, 604 tochange the filtering as appropriate.

FIG. 13 shows a block diagram of an example audio filter 1300 toimplement the first and second mid-range filters 622, 624, 630, 632 ofFIG. 6. The example audio filter 1300 of FIG. 13 receives an audiosignal and outputs filtered audio signals to the mid-range speakers(e.g., an outer mid-range speaker, the mid-range speakers 606, 608, 610,612 of FIG. 6). In particular, the example FIG. 13 may be used to filteraudio signals when the MTM speakers 602, 604 of FIG. 6 are in a verticalorientation.

On receiving the input audio signal, a second-order low-frequency (LF)shelf filter 1302 is applied. The example second-order LF shelf filter1302 has a cutoff frequency of 100 Hz, a quality factor (Q) of 0.707,and a gain of 4.5 dB, and increases the gain of the audio signal forfrequencies below the cutoff frequency. The Q of a filter refers to thedamping and/or resonance of a filter. The resulting signal 1303 is thenapplied to a second-order bandpass shelf filter 1304, which has a centerfrequency of 1.9 kHz, a Q of 1.2, and a gain of −5.0 dB. The bandpassshelf filter 1304 attenuates a band of frequencies centered on 1.9 kHz.The signal 1305 from the bandpass shelf filter 1304 is input to afourth-order low-pass filter 706, which has a cutoff frequency of 3.0kHz and a Q of 0.5. The example low-pass filter 1306 attenuates thesignal for frequencies higher than 3.0 kHz. The signal 1307 from thelow-pass filter 1306 is input from the low-pass filter 1306 to a dynamicbass boost filter 1308 and a limiter 1310. The example filter 1300outputs the filtered signal 1311 to an amplifier (e.g., the amplifier416) and/or to a mid-range speaker (e.g., the mid-range speaker 606).

While the example filter blocks 1302-1310 are shown in the orderillustrated in FIG. 13, the blocks 1302-1310 may be applied in differentways to achieve identical, similar, or different filtering.Additionally, the example center and/or cutoff frequencies, Q values,and/or gains applied by the example filter blocks 1302-1310 may bemodified to change a frequency response of the example audio filter1300.

In view of the foregoing, it should be apparent that disclosed examplesystems, methods, and apparatus can be used to provide an MTM speakerarrangement having improved audio quality and perception. Examplesystems, methods, and apparatus apply different filtering to audiosignals for output by different mid-range speakers based on theorientation of the MTM speaker arrangement and/or the configuration ofthe speakers in a multiple-device arrangement.

Various inventions have been described in sufficient detail with acertain degree of particularity. It is understood to those skilled inthe art that the present disclosure of embodiments has been made by wayof examples only and that numerous changes in the arrangement andcombination of parts can be resorted without departing from the spiritand scope of the present disclosure as claimed. While the embodimentsdiscussed herein can appear to include some limitations as to thepresentation of the information units, in terms of the format andarrangement, the embodiments have applicability well beyond suchembodiment, which can be appreciated by those skilled in the art.Accordingly, the scope of the present disclosure is defined by theappended claims rather than the forgoing description of embodiments.

I claim:
 1. A playback device comprising: a first audio speaker; asecond audio speaker; one or more processors; and tangible,non-transitory computer-readable medium having stored thereoninstructions that, when executed by the one or more processors, causethe playback device to perform functions comprising: based on a playbackconfiguration of the playback device, identifying a first audio filterand a second audio filter, wherein the first audio filter is configuredto have a first frequency response, wherein the second audio filter isconfigured to have a second frequency response; processing audio contentaccording to the first audio filter to produce a first audio output;processing the audio content according to the second audio filter toproduce a second audio output; and causing (i) the first audio speakerto render the first audio output and (ii) the second audio speaker torender the second audio output; wherein the second frequency response ofthe second audio filter compensates for interference between the firstaudio output rendered by the first audio speaker and the second audiooutput rendered by the second audio speaker.
 2. The playback device ofclaim 1, wherein the first audio speaker and the second audio speakerare mid-range speakers having a same audio characteristic.
 3. Theplayback device of claim 1, wherein the second frequency responsecompensates for the interference by dominating the first frequencyresponse.
 4. The playback device of claim 1, wherein the functionsfurther comprise: determining an orientation of the playback device, andwherein identifying the first audio filter and the second audio filtercomprises identifying the first audio filter and the second audio filterfurther based on the orientation of the playback device.
 5. The playbackdevice of claim 1, wherein the playback configuration comprises one of:an individual configuration, a stereo pair configuration, and aconsolidated configuration.
 6. The playback device of claim 1, whereinthe first audio filter comprises a low-pass filter having a first cutofffrequency, and wherein the second audio filter comprises a low-passfilter having a second cutoff frequency that is higher than the firstcutoff frequency.
 7. The playback device of claim 1, wherein the secondaudio filter comprises a high frequency shelf filter that provides again above a cutoff frequency of the first audio filter.
 8. The playbackdevice of claim 1, further comprising a third audio speaker positionedbetween the first audio speaker and the second audio speaker. 9.Tangible, non-transitory computer-readable medium having stored thereoninstructions that, when executed by one or more processors of a playbackdevice, cause the playback device to perform functions comprising: basedon a playback configuration of the playback device, identifying a firstaudio filter and a second audio, wherein the first audio filter isconfigured to have a first frequency response, wherein the second audiofilter is configured to have a second frequency response; processingaudio content according to the first audio filter to produce a firstaudio output; processing the audio content according to the second audiofilter to produce a second audio output; and causing (i) the first audiospeaker to render the first audio output and (ii) the second audiospeaker to render the second audio output; wherein the second frequencyresponse of the second audio filter compensates for interference betweenthe first audio output rendered by the first audio speaker and thesecond audio output rendered by the second audio speaker.
 10. Thetangible, non-transitory computer-readable medium of claim 9, whereinthe first audio speaker and the second audio speaker are mid-rangespeakers having a same audio characteristic.
 11. The tangible,non-transitory computer-readable medium of claim 9, wherein the secondfrequency response compensates for the interference by dominating thefirst frequency response.
 12. The tangible, non-transitorycomputer-readable medium of claim 9, wherein the functions furthercomprise: determining an orientation of the playback device, and whereinidentifying the first audio filter and the second audio filter comprisesidentifying the first audio filter and the second audio filter furtherbased on the orientation of the playback device.
 13. The tangible,non-transitory computer-readable medium of claim 9, wherein the playbackconfiguration comprises one of: an individual configuration, a stereopair configuration, and a consolidated configuration.
 14. The tangible,non-transitory computer-readable medium of claim 9, wherein the playbackdevice further comprises a third audio speaker positioned between thefirst audio speaker and the second audio speaker.
 15. A methodcomprising: based on a playback configuration of a playback device,identifying by the playback device, a first audio filter and a secondaudio, wherein the first audio filter is configured to have a firstfrequency response, wherein the second audio filter is configured tohave a second frequency response; processing by the playback device,audio content according to the first audio filter to produce a firstaudio output; processing by the playback device, the audio contentaccording to the second audio filter to produce a second audio output;and causing by the playback device, (i) the first audio speaker torender the first audio output and (ii) the second audio speaker torender the second audio output; wherein the second frequency response ofthe second audio filter compensates for interference between the firstaudio output rendered by the first audio speaker and the second audiooutput rendered by the second audio speaker.
 16. The method of claim 15,wherein the first audio speaker and the second audio speaker aremid-range speakers having a same audio characteristic.
 17. The method ofclaim 15, wherein the second frequency response compensates for theinterference by dominating the first frequency response.
 18. The methodof claim 15, wherein the functions further comprise: determining by theplayback device, an orientation of the playback device, and whereinidentifying the first audio filter and the second audio filter comprisesidentifying by the playback device, the first audio filter and thesecond audio filter further based on the orientation of the playbackdevice.
 19. The method of claim 15, wherein the playback configurationcomprises one of: an individual configuration, a stereo pairconfiguration, and a consolidated configuration.
 20. The method of claim15, wherein the playback device further comprises a third audio speakerpositioned between the first audio speaker and the second audio speaker.